Genetic Disease: Prevalence

Abstract

Although monogenic diseases are considered to be rare, some are relatively frequent either in large parts of the world or
in more delineated regions. Often, the relative high frequency is limited to some sub‐populations or even small communities.
Various processes influence the prevalence of genetic diseases in the population, in particular the mutation rate, selection
and founder effect with genetic drift. In some genes, the rates of new mutations are high, and the disorder is frequent, often
appearing as sporadic. A selective advantage to carrier of a genetic trait will lead to an increased frequency of the disease
as it has been observed for sickle cell disease in which the carrier status protects from malaria. A relative isolation of
a population that expands rapidly may lead to an increased frequency of genetic traits due to a founder effect.

Key Concepts

In general individual genetic diseases are rare, however, the total number of individuals affected with genetic diseases
is large.

High mutation rate of a specific gene may be responsible for the high prevalence of the corresponding disease.

A genetic disease may be prevalent as a result of selection since the mutation increase the fitness of the carrier.

Genetic isolation of a population may lead to the high frequency of genetic diseases as a result of a founder effect with
genetic drift.

The genetic isolation of a population may be caused by geographic conditions (in the past), religion or consanguinity.